Molecular sieve 13-x catalyzed isomerization of alpha-pinene-improvement of catalyst activity

ABSTRACT

A method for producing dipentene is given whereby a terpene containing feed is isomerized at a temperature of between 140* and 200* C. in the presence of an alkali metal containing aluminosilicate catalysts of the 13X-type which has been activated by water extraction.

United States Patent Davis 51 Oct. 3, 1972 [54] MOLECULAR SIEVE l3-X CATALYZED [56] References Cited ISOMERIZATION OF ALPHA-PINENE- UNITED STATES PATENTS IMPROVEMENT OF CATALYST ACTIVITY 2,382,641 8/1945 Kharasch et al. ..260/675.5 1 2,882,244 4/1959 Milton ..252/455 [72] Inventor: Curry Beach Davis, Panama City, 3,270,075 8/1966 Derfer et al. ..260/675.5 Fla. 32 401 H 3,377,400 4/1968 Wise....; ..260/668 73 I A Ch C m an New 3,642,928 2/1972 Davis ..260/675.5 I I a or p 3,655,803 4/1972 Miller ..260/675.5

[ Filedi J n 1971 Primary ExaminerDelbert E. Gantz Assistant Examiner -G. E. Schmitkons [2| 1 Appl' 148398 Attorney-James H. Laughlin, Jr.

Related US. Application Data ABSTRACT [63] Continuation-impart of Ser. No. 845,431, July 28 1969 abandoned A method for producing dlpentene is given whereby a terpene containing feed is iso'rnerized at a temperature of between 140 and 200 C. in the presence of an al- [52] CL 7 208/DIG' kali metal containing aluminosilicate catalysts of the 51 1m. 01 ..C07c 13/00, C09f 3/02, C0lb 33/28 gf' whlch has been mated by water cmac' [58] Field of Search ..260/675. 5

5 Claims, 6 Drawing Figures WATER 2501. r5

FM 5 FREQ; g r fl TERPENE CATALYST I we 7 STILL /a #25; 6- FILTER PRESS FILTER CAKE 1 CALCl/VED VACUUM ZEOL/TE STRIPPER -9 PATENTEnnma I972 I 3,696,164

' sum 1 or 6 WA TEE ZEOL/TE 2 i 3 4 J v FILTER CATALYST PRESS YER sro/mas TERPE-NE CATALYST mowers 7 I STILL /8 HOLD 1 TANK FILTER PRESS FILTER 04x5 cALcm/Eo VACUUM CAL 0mm? ZEOL/TE .STRIPPER 9 I I E I INVENTOR.

CURRY BEACH DAV/5 ATTORNEY PERCENT YIELD PATENTEDncra m2 sum 3 [IF 6 PINE IVE CA MPHE NE CUR Y BEACH DAV/5 ir TOR/V5) PATENTEDnm 3 I972 SHEET l UF 6 DIPE/VTE/VE PINE IVE M E M M C 7' E RP/IV 0L E NE Q Hui k EMUQNQ REACT/0N TIME (HRSJ v INVENTOR. 01mm BEACH DA 103 PATENTED T 3 I973 SHEET 5 BF 6 D/PE/VTENE CA MPH E IVE TERP/NOL ENE REACT/O/V TIME (HRSJ INVENTOR.

m n V4 2 w n m W; a

PATENTEDUEI 3 I972 SHEEI 6 BF 6 CAMPHE/VE REACT/0N TIME (HRS. I

INVENTOR. cum) BEACH DA v/s BY Ma ATTORNEY This application is a continuation-in-part of application Ser. No. 845,431, filed July 28, 1969, now abandoned.

This invention relates to an improved process for the isomerization of terpenes generally and in particular, turpentine, a-pinene, and B-pinene. More particularly, it relates to the production of dipentene by isomerization of terpene containing feed by means of heating in the presence of a prepared selective catalyst.

Dipentene is an important article of commerce and is in great demand for the production of terpene resins which are used in hot melt coatings, adhesives,.and the like. The prior art shows many examples of isomerizing a-pinene. For example US. Pat. No. 2,382,641 issued to Kharasch and Reynold teaches the conversion of optically active a-pinene to limonene which is the optically active form of dipentene. According to the patent this is accomplished by heating with organic acids, such as benzoylbenzoic or salicyclic acids, in the presence of organic acid amides, such as formamide or acetoamide, at temperatures of 140 to 200C. for 15 to 50. hours. The process of the present invention is advantageous in that the employment of expensive organic acids and amides is avoided and isomerization is effected in a few hours resulting in excellent yields.

Frilette and WeissU.S. Pat. No. 3,143,222, teach the use of an activated 10X'zeolite to reduce-polymer formation in the isomerization of a pinene which under their conditions has been found to yield predominant yields of camphene. In discussing the activity of 13X molecular sieves in thelournal of Physical Chemistry, Vol. 64, page 382, Weiss and Frilette state that apinene undergoes no reaction when refluxed with the Na form 13X Zeolite], but is converted extensively to camphene by the Ca salt [10X zeolite].

U.S. Pat. No. 3,270,075 issued to Derfer and Bordenca teaches the isomerization of a-pinene to a dipentene-rich isomerizate with a 10X or 13X zeolite at temperatures in the range of from about 65 to about 100 C. This patent specifically teaches, however, that the use of higher temperatures is detrimental to the production of dipentene. For example, at Column 8, lines 24 and following, it is stated that when temperatures of about 135 to 154 C. are employed, considerably more camphene is produced and in most instances camphene becomes the predominant product. Furthermore, in Example 1, at Column 6, line 20, it is stated that when a-pinene is treated at 150 C. with a 13X molecular sieve catalyst, the isomerizate' is found to contain only 10% of the desired dipentene product.

It is an object of this invention to provide a simple process for producing high yields of dipentene in an economic manner. A further object is to provide a process for producing dipentene wherein the amounts of undesirable by-products are minimized. These and other objects of the present invention will become apparent from the full reading of the ensuing specification and examples.

In copending application Ser. No. 130,120, filed Apr. 1, 1971 (Case No. 24,083) which was a continuation-in-part of application Ser. No. 845,432, filed July 28, 1969, it is shown that dipentene may be produced in satisfactory amounts by employing an isomerization reaction in the presence of an isomerization catalyst at high temperatures. It has now been unexpectedly found that high yields of dipentene can be obtained by isomerizing a terpene containing feed at high temperatures using a selective and improved alkali metal-containing alumino-silicate catalyst of the 13X type. This finding is particularly surprising since high yields of dipentene may be produced when employing very low amounts of catalyst. Furthermore, only minor amounts of byproducts such as camphene are found.

In accordance with this invention a terpene or pinene containing feed which may include a-pinene, B-pinene, or turpentine is isomerized in the presence of less than about 10 percent of a prepared zeolite catalyst of the 13X type.

Zeolite X can be represented in terms of mole ratios of oxide as follows:

1.01:0.2 M 0 A1 0 2.5i0.5 SiO y H O wherein M is an alkali metal and y is a value from 0 to 8 depending on the identity of the alkali metal and the degree of hydration in the crystal. The sodium form for example may be represented as follows:

0.9 Na O A1 0 2.5 SiO 6.1 H 0.

Typically the anhydrous synthetic sodium zeolite of the X-type has a composition of Na (AlOhd 2),, (SiO and an effective pore diameter of about 13 Angstroms. The crystal structures are such that they have a large number of pores characterized by exceptionally uniform size. As sold commercially, these catalysts are in aqueous slurry or substantially dehydrated form normally having a water content of about 1%. In my invention it is surprising that only the sodium zeolite may be employed and that the potassium and lithium sieves which have similar structures and characteristics may not be used. The alkali metal aluminosilicates employed in the present invention are further described in a number of U.S. Patents, including Nos. 2,882,244 and 3,140,249.

Surprisingly, it has been found thatby pretreating the catalyst prior to the isomerization reactionan unexpectedly high yield of product is obtained. Moreover, by pretreating the catalyst, its activity can be substantially enhanced and improved process characteristics result. It has been unexpectedly found that the sodium-containing aluminosilicate catalyst may be effectively pretreated by extracting the same with water to enhance its activity. By water extraction, it is meant that the catalyst is mixed with large volumes of water and washed. It has been found that be mixing the catalyst with a relatively high volume of water as compared with slurrying wherein small volumes of water are used, that is, from about more than one to about fif teen times the volume of water based upon the catalyst mixed therein and preferably from about two to about ten times, the catalyst may be substantially activated. Typically, the molecular sieve catalysts employed in this invention are washed or admixed from at least 1 to about 10 times with large volumes of water which are usually greater than an equal volume percent of catalyst and preferably from about 2 to 10 times the volume of catalyst being activated.

While I do not wish to be bound to any theoretical considerations, it is my belief that the presence of free sodium metal cations hinders the isomerization reaction. By washing the catalyst certain sodium metal cations which are loosely attached or present on the surfaces of the catalyst are removed thus bringing the surface of the catalyst into substantial equilibrium with the effluent wash water. The removal of these available alkali metal cations reduces the potential ion hinderence to the isomerization reaction.

The wet catalysts can be dried at temperatures of about 150 to about 600 C. but preferably about 300 C., so as to obtain a catalyst having a water content of about 2 to about 6% and preferably 4% for use in the process of the present invention.

It has surprisingly been found that when small amounts of the prepared catalysts are used in the high temperature isomerization reaction, an unexpected high amount of dipentene can be produced. In fact, I have found that dipentene can be produced in predominant amounts while by-products and undesirable reaction products which are usually formed in isomerizations of this type can be minimized and in some cases completely avoided.

In one embodiment of this invention, a pin ene is heated at reflux with less than about based upon the weight of the feed of a pretreated activated 13X molecular sieve zeolite catalyst which had been washed 3 times with fresh effluents of water equaling 10 times the catalyst volume and then subsequently dried at a temperature of 300 C. until a moisture content of about 4% was obtained. The isomerization reaction may proceed for any desired length of time but it is usually limited to from about I to hours. The resulting isomerizate is then filtered to remove the molecular sieves which are then recycled and the isomerizate is fractionated to separate the desired dipentene from other undesirable products.

The isomerization process of the present invention is generally carried out at temperatures of from about 140 C. to about 200 C. Preferred reaction temperaturcs are in the range of 150 to about 175 C. In general, reaction timcs are from about 0.5 to 15 hours. Preferable reaction times are from 2 to 4 hours. The catalyst employed is an activated sodium X-type sieve of the l3X-type which has been activated as discussed above. The amount of catalyst employed may be from about 0.1 to about 5% based upon the weight of the feed for normal operations. However, I have found that dipentene may be efficiently produced by employing from about 0.1 to about 2% catalyst. The process may be carried out either batch-wise or continuously, and under autogeneous, elevated or reduced pressures.

The invention may be further understood by reference to the figures, in which FIG. 1 is a flow diagram of the process,

FIG. 2 shows the reaction conversion in comparison to the drying temperature of the catalyst,

FIGS. 3 to 6 show product constituents without a pretreatment of catalyst and with varying amounts of moisture on the pretreated catalyst.

As shown in FIG. 1, the zeolite catalyst is given a pretreatment by extraction with water in mixer 1, filtered in filter press 2, dried in dryer 3 and stored at 4.

The pretreated catalyst and terpene feed are fed to the reactor 5 where the reaction takes place under the conditions previously recited, after which the catalyst and product mixture is separated in filter press 6. The catalyst goes to a vacuum stripper 9 for removal of any remaining product and then to calciner 10 to be heated and recycled to the process.

The isomerized product from filter press 6 containing predominately dipentene but also minor amounts of terpinolene and camphene is recycled through a holding tank 7 which also receives the effluent from stripper 9. The combined product from tank 7 is then distilled to separate the various fractional products.

The following examples further illustrate the present invention and are not intended to limit the scope thereof in any manner. Reference numerals in the examples refer to FIG. 1. Examples 1 to 5 disclose the results obtained with a slurried catalyst. Example 6 shows the results obtained with an extracted catalyst. All parts are by weight unless otherwise stated.

EXAMPLE I 500 pounds of 13X molecular sieves (Linde Division of Union Carbide Corporation) was charged to kettle 1 containing 200 gallons dionized water. The mixture was then slurried for 30 minutes and filtered through filter press 2, the effluent being sewered. The filter cake was transferred to drier 3 where it was dried 16 hours at 300 C. prior to transfer to catalyst storage 4.

EXAMPLE 2 Kettle 5 was purged with inert gas, preferably nitrogen, prior to charging 3,900 pounds of a-pinene. 39 pounds of the catalyst of Example I was then added while agitating at 250 rpm. The port was then closed, and the temperature was raised rapidly. The mixture began to reflux at 162 C. and, within 5 hours, had reached l72.5 C. Full cooling water was then turned on. The cooled mixture was pumped through filter press 6, with the isomerizate going to holding tank 7 and the filter cake to vacuum stripper 9. The dried filter cake was transferred to calciner 10 where it was calcined 1 hour at 600 C. before being returned to storage.

The isomerizate, on fractionation in still 8 yielded 2,254 pounds dipentene, 407 pounds terpinolene, 625 pounds camphene, 175.5 pounds unreacted a-pinene, and 358 pounds other terpenes.

EXAMPLE 3 The procedure of Example 2 was repeated in every detail except that ,B-pinene was used as the feedstock.

The isomerizate, on fractionation, yielded 2,l06 pounds dipentene, 443 pounds terpinolene, 371 pounds a-pinene, 404 pounds camphene, and 240 pounds other terpenes.

EXAMPLE 4 The procedure of Example 2 was followed in every detail, except that sulfate terpentine was used as the feedstock.

The isomerizate, on fractionation, yielded 2067 pounds dipentene, 710 pounds camphene, 472 pounds terpinolene, 421 pounds a-pinene, 31 pounds fl-pinene and pounds other terpenes.

To determine the influence of the temperature at which the catalyst was dried and, indirectly, of moisture content on the rate of the isomerization reaction, the following series of experiments was carried out.

Hydrated 13X catalyst was dried at various temperatures ranging from ambient temperature to 600 C., and the dried catalyst thus obtained was evaluated with regard to its activity towards a-pinene in the following manner.

2.0 g. of catalyst was contacted with 100 g. of ozpinene, and the resulting mixture was heated isothermally under nitrogen at 160 C. This amounts to 2% catalyst based on the a-pinene. Samples were withdrawn periodically and analyzed. The data ob tained is illustrated in Table I.

TABLE 11 Number of Reaction Max. Yield Figure Extractions Time of dipentene 3 None I 4.0 hrs; 65% 6.0 hrs. 4 1 1.8 hrs. 63% 2.5 hrs. 5 3 1.1 hrs. 63%- 1.5 hrs. 6 6 0.6 hrs. 59% 0.7 hrs.

Reaction time to 10% a-pinene in isomerizate Using the optimum drying temperature for the catalyst, as shown in Example 5, of 325 C., the catalyst was extracted a variable number of times before drying. The effect of multiple extractions is shown in Table II and FIGS. 3 to 6. FIGS. 3 to 6 correspond to the TABLE I Eflect of H10 concentration on reactivity of molecular sieve 13X during isomerization of a-pinene] Water Time Catacontent Reac (min.) Catalyst tion to attain Percent yield of products based on lyst conc., catalyst temp., reaction 1 1% 2 2% 3 3% 4 4% 5 5% p1n ene consumed at maximum source percent (percent) C. temp. hr. hrs. hrs. hrs. hrs. hrs. hrs. hrs. hrs. hrs. hrs. indicated conversion. A 2 28.0 160 120 30.0 38.7 45.6 49.3 51.4 Dipentene, 67.8; camphene, 18.4;

terpinolene, 8.9. B 2 10.5 160 60 41.2 52.6 61.3 68.8 73.3 Dipentene, 66.6; eamphene, 18.2;

- terpinolene, 9.4. C 2 9.4 160 55.9 71.2 80.4 86.7 90.7 94.2 Dipentene, 63.2; camphene, 17.6;

. terpinolene, 11.0. D 2 5.3 160 13 75.3 87.8 91.6 94.2 Dipentene, 62.2; camphene, 18.0;

terpinolene, 11.4. E 2 4.3 160 12 86.6 91.8 94.8 Dipentene, 63.8; camphene, 18.3;

terpinolene, 11.1. F 2 4.6 160 12 53.5 71.6 80.8 87.4 92.7 94.8 Dipentene, 64.0; camphene, 17.5; terpinolene, 10.8.

A=Catalyst slurry air dried at ambient temperature. B=A (above) dried at 150 C. G=A (above) dried at 200 C. D=A (above) dried at 2150 0. %=2 (above) dried at 300 (above) dried at 600 This example is further illustrated by FIG. 2 which illustrates that there is an optimum drying temperature for best product yield on an equal reaction time basis. of two hours, which lies between about 300 and 350 C. This is also shown byTable I, although the rate of conversion for all of the runs of .Table I is greatly superior to prior art processes.

EXAMPLE 6 Ten grams of calcined molecular sieve 13-X powder catalyst (Union Carbide Corp.) were slurried for about 10 minutes in 100 ml. of distilled water. The molecular sieve catalyst was recovered on a Buchner funnel and then dried at 325 C. for 17 hours. Samples of the catalyst were also prepared by repeating the extraction step three and six times prior to drying at 325 C. A control catalyst was prepared by wetting the calcined molecular sieve prior to drying.

The performance of the fourcatalysts samples was evaluated in batch isomerizations of a-pinene. Two hundred grams of a-pinene and two gm. of catalyst were charged to a 500-ml., three-neck flask fitted with a gas inlet tube, thermometer and reflux condenser. This amounted to 1% catalyst by weight of a-pinene. The flash was flushed with nitrogen and the oz-pinene heated to reflux. Aliquots were removed during the reaction for gas chromatographic analyses. The results were as shown in Table II.

number of extractions as shown in the Table. It will be seen that miltiple extractions of the catalyst greatly increase the rate of conversion with only a negligible decrease in dipentene yield.

I claim:

1. A method for producing dipentene comprising isomerizing a pinene-containing feed at a temperature from about to about C. for from about 0.5 to 4 hours in the presence of from about 0.1 to about 5% based upon the weight of the feed of an activated molecular sieve zeolite catalyst of the l3X-type containing sodium ions, said catalyst being activated by water extraction comprising admixing and washing the catalyst from one to about ten times with from about one to aboutlS times the volume of water based upon the volume of catalyst being activated, and drying at a temperature of from about 150 to about 600 C. until themoisture content of the activated catalyst is from about2 to about 6%.

2. The method of claim 1 wherein the feed is selected from the group consisting of a-pinene, B-pinene, and turpentine.

-3. A method for producing dipentene comprising isomerizing a terpene containing feed at a temperature from about 140 to about 200 C. for more than about 0.5 hours in the presence of less than about 10% based upon the weight of the feed of an activated zeolitic molecular sieve catalyst of the 13X-type said catalyst tracted from one to ten times with from about 2 to about 10 times the volume of water based upon the catalyst volume, and dried at a temperature from about 150 to about 600 C., until the moisture content of the feed is selected from the group consisting of a-pinene, 5 catalyst is about 4%.

B-pinene, and turpentine.

5. The method of claim 3 wherein said catalyst is ex- 

2. The method of claim 1 wherein the feed is selected from the group consisting of Alpha -pinene, Beta -pinene, and turpentine.
 3. A method for producing dipentene comprising isomerizing a terpene containing feed at a temperature from about 140* to about 200* C. for more than about 0.5 hours in the presence of less than about 10% based upon the weight of the feed of an activated zeolitic molecular sieve catalyst of the 13X-type said catalyst being activated by admixing and washing with greater than an equal volume percent of water until the catalyst is activated, and then subsequently dried.
 4. The method of claim 3 wherein the predominant feed is selected from the group consisting of Alpha -pinene, Beta -pinene, and turpentine.
 5. The method of claim 3 wherein said catalyst is extracted from one to ten times with from about 2 to about 10 times the volume of water based upon the catalyst volume, and dried at a temperature from about 150* to about 600* C., until the moisture content of the catalyst is about 4%. 